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If a+b=7 and a^3+b^3=91, find the value of ab |
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Answer» Answer: given, a + b = 7 and a³ + b³ = 91 since, a³ + b³ = ( a + b)³ -3ab( a + b) => 91 = 7³ -3ab× 7 => 91 = 343 - 21AB => 21ab = 343 -91 => 21ab = 252 => ab = 253/21 = 12 so, ab = 12. |
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